Method of making dry rectifiers



Feb. 19,1946v W. C. ELLIS ETAL METHOD OF MAKING DRY RECTIFIERS Filed Oct 24, 1942 PREPARATION OF BACK ELECTRODE APPLICATION OF SELENIUM TO BACK ELECTRODE HEAT TREATMENT AT II 0C HEAT TREATMENT AT 2IO-2I7 C FLUID TREATMENT QF' SELENIUM SURFACE APPLICATION OF FRONT ELECTRODE ELECTRICAL FORMING HEAT TREATMENT AT 70-IOO C I-5 HOURS ELECTRICAL REFORMING lNI/EA/7ORS1' ELL/S A. G. SOUDE/V B) v ATTORA ZI I under mechanical pressure.

Patented Feb. 19, 1946 more!) STATE-S 2,395,259 Y MAKHG may areas Mirrnon or ATEN'E FFiCE William C. Ellis ilwaplewood; and Alexander G.

Souden, Summi N. J phone Laboratories, In

assignors to Bell Telecorporated, New York,

- Y., a corporation of New York Application October 24, 1942, Serial No.

Claims. (Cl 175-366) vided into two stages. prises heating the unit to The first stag comabout 110 C. while the selenium The second stage of heat treatment is performed at a temperature ing point (218 C.) of the selenium, e. g., between 210 and 217 C. After the heat treatment the surface of the selenium may be treated 'by exposingit for a short Lrzne' to a vapor of selenium alkaline halides or other suitparticularly to selenium rectifiers and rectification ratio of slightly below the meltthe high resistance or reverse direction. The forming current should be limited in order to avoid burning out of the unit. As the reverse increases during the formto about forming as completed rectifier to increase the value of the rectification ratio by increasing the reverse resistance. This is believed to be with the usual nomenclature applied to the mak- Careful performance a unit having a relatively good ratio of reverse to forward resistance.

,An object of this invention is to increase the reverse resistance of a selenium rectifier unit characteristics after completion.

A feature of this invention resides in subjecting the formed rectifier units to an additional heat treatment at from to C. for from 1 to 5 hours and then reforming the units.

The invention and the foregoing and other objects and treatment is applied. heated at'from 70 to 100? C. for from 1 to 5 hours. This may be done by distributing a plurality of units on a suitable carrier such as a Although this invention has been disclosed by metal plate and inserting them in an oven, means of illustrative embodiments thereof, it is which has been brought up to the required temnot intended that it be limited thereby, but by perature. The temperature is maintained at the the scope of the appended claims only. value chosen, for the whole time of treatment 5 What is claimed is: and then the units are removed and allowed to 1. The method of making a selenium rectifier cool. Since the, efiect of this treatment appears unit with a high reverse resistance and large to be a function of both. time and temperature,- rectification ratio that comprises applying a n a ru i ha a longer time is employed amorphous selenium to a suitable electrode, heat for the lower temperatures and a shorter time treating t n rt th amorphous selenium to for the hi her t mp Imp crystalline sel'enium, providing the unit with an that is, increased, inthe reverse resistance may outer contact, forming .the unit by application be obtained o er e whole of e given thereto oi avoltage inthe reverse direction, then perature range for time periods up to and infurther heat treating the unit at a temperature eluding 5 hours. At the h g ef temperatures, of from '70 to 100 C. for a period of from 1 to 5 i. e., 95 C. and above, if the time is extended hours, d then reforming the t, by further beyondabout' 3 hours, the forward reslstafflce application thereto of a voltage in the reverse may increase so much that there is no net 1mdiremmn,

provement in rectification ratio. In the term The methdd of u a Selenium rectifier perature range from to 85 0., inCleaS a reverse resistance and large in forward resistance relatively slight and r tifi ati n ratio, that comprises applying this cmipled 71th a @0115 defame mmeaSe m amorphous selenium to a. suitable ele' trade-neat verse-resistance gives an improved rectification treating to convert the amorphous selenium'm,

'fl F those tempera-lures the crystalline selenium, providing th unit with an g'l'eater if time ute cntact forming the unit I y n 311101115 unt o mfludmg 5 mum A thereto of-a voltage in the reverse direction, then wilt-hour treatment at c-appeers to have further heat treating the unit at a temperature practlcallyno effect on thefortvardv resistance of from 0 t 95 Q for period of from ,v 1 3.3 whil increasing the reverse resistance 'cOnSidur and than refo ming the it by m a w A temperatures above u -9 plication'thereto or avoltsge in the reverse mreocare must be taken to avoid reaction between m the selenium and the front contact. This is 3 The method of aking l i m rum,

imtiwmfly true Where the front Fontwt is unit having a high reverse resistance and lam adherent boating f low l i roint metal or rectification ratio that comprises applying amen 11 9: r mp e, with a tin bismuth-eadphous seleniumto asuitabie electrode,'heat treatnuum alloy, adherent contact, which melts at mg to convert, the amorphous seien'mm to about 1'02 0.; the treat ent could be carried cyystamne selenium, providing the unit t upto 100 C. without meltingthe contact but outer Contact "forming the t by appflcation there is danger of reaction between the contact thereto of a velmge m the reverse m um alloy-and the selenium when the melting p int 40 f ther-heat treating the unit at'atemperatnreo'f is aw about 15 0. for a period of about 5 hours and After this additional heat treatment, the race than. reforming the un t by further application @f j h are a ain subaecteu'to the el r thereto or a voltage in the reverse direction. m s a ment. by passingcurrent throug 4. The method of improving the rectification them in therev' rseiii at controlled ratio of selenium rectifier units by increasing the g f m idr-amtfzoimmutes at about reverse resistance thereof without appreciably 20 volts in the reverse direotion'haish'e n found changing the forward resistance, that compri es to give satisiactory -results.

subjecting completely formed rectifier units to a 53 x i t Fr u obtamable by temperature of from to to 100 C. for a period of this method, a treatment at from 96 to 95 C. for from 1 to 5 hours, and then reforming the units. 1% hours f l w d by r'eiomims at about by further application thereto or avoltage in the volts increased the rectification 'ratio in the orreverse direction, the time period within the. in (let, a! 90 percent with -'a reduction or less than dicate'd range being short for the higher temperalO i cent i the Value of f rw r current. tures and long for the lower temperatures.

Treatment'at W5 G-fGY about 8 hours wlthia 55 5. The method of making a selenium rectifie subsequent zo-voitre'iorming increased the reounit with a high reverse resistance and lam tifl'catldn ratio by about '70 per cent with no r ctification ratio that comprises applying amornoticeable reduction inrro'rwara current. It is phou's seleniumtoa suitable electrode, heat treatthus seen that this process may be performed mg to convert the amorphous selenium to cry t to produce a very large increase in rectification to line selenium, providing the unit with another ratio with very little less in forward current or contact, forming the unit by application theret a somewhat smaller but nevertheless'marked inof; a voltage in the reverse direction, then fincrease-in rectification' ratio with no loss of iorther heat treating the unit at a w'ar'd C. for a'period of about 1% hours, and then re- Ihaddition tothe o'nthe 'absolute valu forming the unit by passing current tnerothroueh of the 'to a-rd -and reverse resistances, it has in the reverse direction under agressure; of'ahm t been round that selenium rectifier-s given a heat 20 Ivolts for about zo'minutes. treatment and then reformed in accordance with this invention are more stable than units prepared in the ordinary manner. That is, there XAND R, (3,, 50mm, appears to be less drift with time for both forward and reverse characteristics. 

